Some reputable companies.. Toshiba, Dell, Sony, Fujitsu, IBM, Gateway, and I think HP is on its way up again. Sony laptops will be more stylish (but overpriced). IBM laptops are usually more business oriented (but very nice). Toshiba and Fujitsu's are good for the value. Dell has great support and reasonable prices (but imo, i think their computers are ugly). Gateway, I have no experience but my cousin has one of their laptops and he hasn't had a problem yet.
I have a Dell centrino laptop (very light) for school use, and an Alienware bulky desktop replacement laptop (10lbs and overheats). Stay away from Alienware (support sucks, overpriced, etc.). If anything Alienware, consider their desktops as they are actually very nice. Dell replaced my faulty CDRW drive immediately and all I had to do is send the broken one within a month or so.
For me, I cant stand using an Apple Macintosh PC. I've been a PC user for such a long time and I can practically do anything that a Mac can dish out on my Windows based computer. But that's just me. Props to Apple for their iPods though.. iPod sales probably saved the company.